Starbucks says guns are no longer welcome at its coffee shops around the world - inside or at its outside seating areas.

In an open letter Tuesday, Starbucks chief executive Howard Schultz said it is "respectfully requesting" that customers no longer bring weapons into the 18,000 outlets it operates in 62 countries, but stopped short of an outright ban.

The message was particularly aimed at U.S. customers. The coffee chain has increasingly become a focal point of the debate over gun rights in the United States, whose Constitution protects gun ownership.

Many U.S. states allow gun owners to openly carry registered weapons in public. Some gun rights advocates have staged "Starbucks Appreciation Days" by showing up at the coffee shops with firearms, which Schultz said is "unsettling and upsetting" for many customers.

The Starbucks executive said, "To be clear: we do not want these events in our stores."

Schultz said the company is not imposing an outright ban to give gun owners "the chance to respect our request." If Starbucks banned weapons, Schultz said he would not be comfortable with putting Starbucks workers in the position of having to confront customers who show up with a gun.